ALS parkinsonism-dementia complex (ALS-PDC) is a neurological disease that can present as classical ALS, an Alzeheimer's-like disorder with associated parkinsonism features, or a combination. It is a cluster of age-dependent neurodegenerative disorders, representing the only widely acknowledged such cluster and may offer vital clues to the etiology of related disorders. We have successfully modeled the disease by feeding washed cycad flour to adult mice, which develop behavioral and histopathological deficits resembling ALS-PDC. The ability to model the disease allows us to ask fundamental questions of great potential impact for related disorders: Which environmental toxins and genetic susceptibilities contribute to neurodegeneration? What is the time course of the behavioral and pathological deficits from initial expo- sure until behavioral end state? How does age affect disease development and progression? Finally, based on the above, can we design prophylactic and early treatment strategies to prevent further neurode- generation? Using our model of ALS-PDC, we will address the crucial questions of (1) neurodegeneration time-line and (2) the impact of neurotoxins as a function of age. To probe these questions, adult male CD-1 mice will be fed washed cycad or the isolated putative cycad toxins, variant steryl glucosides. A detailed time-line of behavioral, morphological, and biochemical events will be studied from initial exposure through to an end state for both groups. To further examine crucial events in the neurodegeneration cascade, neural cells will be examined in a tissue culture preparation during and following exposure to steryl glucosides. The proposed age effects study will examine two aspects: cycad neurotoxin-induced behavioral and pathological effects as a function of age over a span of 1 to 18 months. In a second series of experiments, we will determine if an early exposure to cycad toxins can exacerbate a late adult expo- sure. These data will provide therapeutic targets to prevent or halt the progression of neurodegeneration.